Pressure Switches - Viessmann VITODENS 200-W B2HA 150 Service Instructions Manual

Start-up and Service
Vitodens 200-W B2HA 112, 150, 399, 530 Service

Pressure Switches

Rear View
GDW1 low pressure gas switch (n.c.)
When the gas pressure rises above 4" w.c. the switch
will open and the burner will operate. When the gas
pressure drops below 4" w.c. the switch will close and
the boiler control will shut off the burner.
GDW2 high pressure gas switch (n.o.)
When the gas pressure rises above 3.5" w.c. the switch
will close and the boiler control will shut off the burner.
If either switch is activated (closed position) the burner
will shut down, but no fault will be displayed on the
control.
Check address 38 in coding 2, if the value is 2 then one
of the switches has been activated (closed).
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